Magnetic disk device and information management method

ABSTRACT

According to one embodiment, a magnetic disk device includes a first disk having a first user data region and a first system area, a second disk having a second user data region and a second system area, a first head that writes data to the first disk, a second head that writes data to the second disk, a first actuator having the first head, a second actuator having the second head, a first controller that controls the first disk, the first head, and the first actuator, and a second controller that controls the second disk, the second head, and the second actuator, wherein the first controller records first information related to the first head and the first disk in the second system area.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2020-153963, filed Sep. 14, 2020, theentire contents of which are incorporated herein by reference.

FIELD

Embodiments describes herein relate generally to a magnetic disk deviceand an information management method.

BACKGROUND

For a magnetic disk device, a side erasure where data is erased canoccur due to the influence of leakage magnetic flux or the like(Adjacent Track Interference: ATI) from the head when data is written.The ATI depends on, for example, the characteristics of the head, thetrack per inch (TPI) setting value, the write current setting value, andthe like. To prevent the side erasure, the magnetic disk device has afunction (refresh function) to rewrite the data of a particular track,when the degree (or the number of times) of influence of leakagemagnetic flux or the like (hereinafter, may be referred to as an ATIcount) from the head, corresponding to the number of times of writingdata to a surrounding track of a particular track, reaches the specifiednumber of counts. The magnetic disk device records and manages the ATIcount as a table in a particular recording region.

Further, in recent years, as the recording capacity of the magnetic diskdevice has increased, the number of magnetic disks has also increased.In order to cope with the increase in the number of magnetic disks, theso-called split actuator magnetic disk device having a plurality ofactuators, for example, two actuators, has been proposed. The splitactuator magnetic disk device includes a plurality of controllers thatcontrols a plurality of respective actuators. The split actuatormagnetic disk device records and manages the number of ATIs for eachactuator as a table in a particular recording region.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a magnetic disk device according to anembodiment.

FIG. 2 is a schematic diagram showing a configuration example of thesystem controller according to the embodiment.

FIG. 3 is a schematic diagram showing an example of the ATI count to beincreased for the surrounding region according to the number of timesdata is written to a particular track 0.

FIG. 4 is a schematic diagram showing an example of the internal logtable.

FIG. 5 is a schematic diagram showing an example of the managementmethod of the internal log table according to the embodiment.

FIG. 6 is a schematic diagram showing an example of the managementmethod of the internal log table according to the embodiment.

FIG. 7 is a flowchart showing an example of the management method of theinternal log table according to the embodiment.

FIG. 8 is a schematic diagram showing a configuration example of thesystem controller according to Modification 1.

FIG. 9 is a schematic diagram showing an example of the managementmethod of the internal log table according to Modification 1.

FIG. 10 is a schematic diagram showing an example of the managementmethod of the internal log table according to Modification 1.

FIG. 11 is a schematic diagram showing an example of the managementmethod of the internal log table according to Modification 1.

DETAILED DESCRIPTION

In general, according to one embodiment, a magnetic disk devicecomprises: a first disk having a first user data region to which userdata is written and a first system area different from the first userdata region; a second disk having a second user data region to whichuser data is written and a second system area different from the seconduser data region; a first head that writes data to the first disk andthat reads data from the first disk; a second head that writes data tothe second disk and that reads data from the second disk; a firstactuator having the first head; a second actuator having the secondhead; a first controller that controls the first disk, the first head,and the first actuator; and a second controller that controls the seconddisk, the second head, and the second actuator, wherein the firstcontroller records first information related to the first head and thefirst disk in the second system area.

Hereinafter, embodiments will be described with reference to thedrawings. It should be noted that the drawings are merely examples anddo not limit the scope of the invention.

Embodiments

FIG. 1 is a block diagram schematically showing a magnetic disk device 1according to an embodiment.

The magnetic disk device 1 includes a head disk assembly (HDA) describedlater, a driver IC 20, a head amplifier integrated circuit (hereinafterreferred to as a head amplifier IC or a preamplifier) 30, a volatilememory 70, a buffer memory (buffer) 50, a nonvolatile memory 80, and asystem controller 130 which is an integrated circuit of one chip.Further, the magnetic disk device 1 is connected to a host system(hereinafter simply referred to as a host) 100. The magnetic disk device1 is a split actuator magnetic disk device that can independently drivea plurality of, for example, two actuators 16 described later. Themagnetic disk device 1 may have more than two actuators 16.

The HDA includes a magnetic disk (hereinafter referred to as a disk) 10,a spindle motor (hereinafter referred to as an SPM) 12, an arm 13 onwhich a head 15 is mounted, a voice coil motor (hereinafter referred toas a VCM) 14. The disk 10 is attached to the spindle motor 12 androtates by driving the spindle motor 12. The disk 10 has, for example,disks 10A and 10B. The disk 10 may have three or more disks. Further,the disks 10A and 10B may each have two or more disks. The arm 13 has,for example, arms 13A and 13B. The arm 13 may have three or more arms.The arms 13A and 13B may each have two or more arms. The VCM 14 has, forexample, VCM 14A and 14B. The VCM 14 may have three or more VCMs. Thehead 15 has, for example, heads 15A and 15B. The head 15 may have threeor more heads. Further, the heads 15A and 15B may each have two or moreheads. For example, the head 15A is mounted on the arm 13A. Further, forexample, the head 15B is mounted on the arm 13B.

The actuator 16 has actuators 16A and 16B. The actuator 16 may havethree or more actuators. The actuators 16A and 16B are mounted on acommon pivot and can rotate independently around the pivot. The actuator16A includes the arm 13A and the VCM 14A. The actuator 16A may include ahead 15A, a driver IC 20, and a head amplifier IC 30. The actuator 16Acontrols the movement of the head 15A mounted on the arm 13A to aparticular position on the disk 10A by driving the VCM 14A. The actuator16B includes the arm 13B and the VCM 14B. The actuator 16B may include ahead 15B, a driver IC 20, and a head amplifier IC 30. The actuator 16Bcontrols the movement of the head 15B mounted on the arm 13B to aparticular position on the disk 10B by driving the VCM 14B.

In the disk 10, a user data region that can be used by a user and asystem area to which information necessary for the system management iswritten are allocated in a region to which the data can be written. Forexample, the disk 10A is allocated a user data region 10A1 and a systemarea 10A2. For example, the disk 10B is allocated a user data region10B1 and a system area 10B2. Hereinafter, a direction orthogonal to theradial direction of the disk 10 is referred to as a circumferentialdirection.

The head 15 has a slider as a main body, and has a write head and a readhead mounted on the slider. The write head writes data to disk 10. Theread head reads the data written to the disk 10. For example, the head15A includes a write head 15WA that writes data to the disk 10A and aread head 15RA that reads the data written to the disk 10A. For example,the head 15B includes a write head 15WB that writes data to the disk 10Band a read head 15RB that reads the data written to the disk 10B.

The driver IC 20 controls the drive of the SPM 12 and the VCM 14according to the control of the system controller 130. In other words,the driver IC 20 controls the drive of the SPM 12 and the actuators 16(actuators 16A and 16B) according to the control of the systemcontroller 130. The plurality of driver ICs 20 may be provided accordingto the number of actuators 16. For example, the driver IC 20 may includea driver IC that controls the drive of the actuator 16A according to thecontrol of the system controller 130 (for example, a microprocessor(Micro-processing unit: MPU) 60A described later), and a driver IC thatcontrols the drive of the actuator 16B according to the control of thesystem controller 130 (for example, an MPU 60B described later).

The head amplifier IC (preamplifier) 30 includes a read amplifier and awrite driver. The read amplifier amplifies the read signal read from thedisk 10 (disks 10A and 10B) to output it to the system controller 130(more specifically, read/write (R/W) channels 40A and 40B to bedescribed later). The write driver outputs a write current correspondingto a signal output from the system controller 130 (for example, the R/Wchannels 40A and 40B described later) to the head 15. The plurality ofhead amplifier ICs 30 may be provided according to the number ofactuators 16. For example, the head amplifier IC 30 includes a headamplifier IC that signal processes the read signal read from the disk10A by the head 15A mounted on the actuator 16A, and a head amplifier IChaving a read amplifier that processes the read signal read from thedisk 10B by the head 15B mounted on the actuator 16B.

The volatile memory 70 is a semiconductor memory from which stored datais lost when power supply is cut off. The volatile memory 70 stores dataand the like necessary for processing in respective units of themagnetic disk device 1. The volatile memory 70 is, for example, adynamic random access memory (DRAM) or a synchronous dynamic randomaccess memory (SDRAM).

The nonvolatile memory 80 is a semiconductor memory that records datastored even when power supply is cut off. The nonvolatile memory 80 is,for example, a NOR type or NAND type flash read only memory (FROM).

The buffer memory 90 is a semiconductor memory that temporarily recordsdata and the like transmitted and received between the magnetic diskdevice 1 and a host 100. It is to be noted that the buffer memory 90 maybe formed integrally with the volatile memory 70. The buffer memory 90is, for example, a DRAM, a static random access memory (SRAM), an SDRAM,a ferroelectric random access memory (FeRAM), a magnetoresistive randomaccess memory (MRAM), or the like.

The system controller (controller) 130 is implemented by using a largescale integrated circuit (LSI) referred to as the System-on-a-Chip (SoC)in which a plurality of elements is integrated on a single chip, forexample. The system controller 130 is electrically connected to thedriver IC 20, the head amplifier IC 30, the volatile memory 70, thebuffer memory 90, the nonvolatile memory 80, and the host system 100.The system controller 130 includes, for example, the system controllers130A and 130B. For example, the system controller 130A is electricallyconnected to the driver IC 20, the volatile memory 70, the buffer memory(buffer) 50, the nonvolatile memory 80, and the system controller 130B.Further, the system controller 130A is connected to the host 100. Forexample, the system controller 130B is electrically connected to thedriver IC 20, the head amplifier IC 30, and the system controller 130A.The system controller 130 may have three or more system controllers 130.

FIG. 2 is a schematic diagram showing a configuration example of thesystem controller 130 according to the present embodiment.

The system controller (controller) 130A includes the read/write (R/W)channel 40A, the hard disk controller (HDC) 50A, and the microprocessor(MPU) 60A. The system controller 130A is electrically connected to thedriver IC 20, the head amplifier IC 30, the volatile memory 70, thenonvolatile memory 80, the buffer memory 90, the system controller 130B,the host 100, and the like.

The R/W channel 40A executes a signal process of read data transferredfrom the disk 10A to the host 100 and write data transferred from thehost 100 in response to an instruction from an MPU 60A to be describedlater. The R/W channel 40A has a circuit or a function of measuring asignal quality of read data. The R/W channel 40A is electricallyconnected to the head amplifier IC 30, the HDC 50A, the MPU 60A, and thelike, for example.

The HDC 50A controls data transfer between the host 100 and the R/Wchannel 40A in response to an instruction from the MPU 60A describedlater. The HDC 50A is electrically connected to, for example, the R/Wchannel 40A, the MPU 60A, the system controller 130B, the volatilememory 70, the nonvolatile memory 80, the buffer memory 90, the host100, and the like.

The MPU 60A is a controller that controls respective units of themagnetic disk device 1. The MPU 60A controls the actuator 16A (VCM 14A)via the driver IC 20 and executes servo control that positions the head15A. The MPU 60A controls a write operation of the data to the disk 10Aand selects the storage destination of the write data. In addition, theMPU 60A controls a read operation of the data from the disk 10A andcontrols the process of the read data. The MPU 60A is connected to eachunit of the magnetic disk device 1. The MPU 60A is electricallyconnected to the driver IC 20, the R/W channel 40A, the HDC 50A, and thelike, for example.

The MPU 60A includes a read/write controller 610A, an internal logmanagement unit 620A, and a refresh processing unit 630A. The MPU 60Aexecutes the process of each of these units, for example, the read/writecontroller 610A, the internal log management unit 620A, and the refreshprocessing unit 630A on the firmware. The MPU 60A may include therespective units, for example, the read/write controller 610A, theinternal log management unit 620A, the refresh processing unit 630A, andthe like as circuits.

The read/write controller 610A controls the read process and the writeprocess of data according to a command from the host 100. The read/writecontroller 610A controls the VCM 14 via the driver IC 20, positions thehead 15A at a target position on the disk 10A, and reads or writes data.Hereinafter, the term “access” may be used including recording orwriting data in a particular region, reading out or reading data from aparticular region, moving the head 15 or the like to a particularregion.

The internal log management unit 620A manages the state of the magneticdisk device 1, for example, the data written to the disk 10 and the datafor confirming the soundness of the head 15 (hereinafter, may bereferred to as an internal log). The internal log includes the data usedin a self-monitoring, analysis and reporting technology (SMART), thedata related to a fault (for example, defect) of the disk 10A, and thedegree or the number of times (hereinafter, may be referred to as an ATIcount) of influence of leakage magnetic flux or the like (Adjacent TrackInterference: ATI) from the head 15A when data is written to theperiphery. The internal log management unit 620A manages the internallog as a table. The internal log management unit 620A develops (disposesor temporarily stores) the internal log table (hereinafter, may bereferred to as internal log table) TBA corresponding to the actuator 16A(the disk 10A, the head 15A, and the system Controller 130A) in avolatile recording region, for example, the volatile memory 70, andperforms the process such as updating. For example, when the internallog table TBA is a table (hereinafter, may be referred to as an ATImanagement table) of the ATI count related to the ATI, every time datais written to a track located in the radial direction of a particulartrack, for example, to a track (hereinafter, may be referred to as anadjacent track) adjacent to the particular track in the radialdirection, a particular number of times, for example, once, the internallog management unit 620A increases the ATI count corresponding to thisparticular track of the internal log table TBA developed to the volatilememory 70 by a particular value, for example, by one. Here, “adjacent”includes not only a state in which data, an object, a region, a space,etc., are disposed in contact with each other, but also a state in whichthey are disposed at a particular interval. When the internal log tableTBA is the ATI management table, and the data is written to theparticular track, the internal log management unit 620A clears the ATIcount corresponding to this particular track of the internal log tableTBA developed to the volatile memory 70, for example, makes the ATIcount zero.

The internal log management unit 620A periodically records the internallog table TBA developed in the volatile recording region, for example,the volatile memory 70, in the non-volatile recording region, forexample, the system area 10A2 of the disk 10A. When the internal logmanagement unit 620A records the internal log table TBA developed in thevolatile recording region, for example, the volatile memory 70, in thenon-volatile recording region, for example, the system area 10A2 of thedisk 10A, the internal log management unit 620A adds a time-stamp to theinternal log table TBA and record it in the system area 10A2 of the disk10A. The time-stamp corresponds to data indicating the time when theparticular data was recorded in the particular recording region. Forexample, the time-stamp is indicated by the total time during which themagnetic disk device 1 is supplied with power (current or voltage).Therefore, the larger the time-stamp, the newer the internal log table,and the smaller the time-stamp, the older the internal log table. Inother words, the internal log table having the largest time-stamp amonga plurality of internal log tables with time-stamps corresponds to thenewest internal log table, and the internal log table having thesmallest time-stamp among a plurality of internal log tables withtime-stamps corresponds to the oldest internal log table.

When the number of commands to be processed by the system controller130A is large, or when the access frequency at which the actuator 16A isdriven and the head 15A accesses the disk 10A is large, that is, whenthe system controller 130A is in a busy state, the internal logmanagement unit 620A writes the internal log table TBA to the systemarea of another disk 10, other than the disk 10A, for example, thesystem area 10B2 of the disk 10B, corresponding to a system controller130 etc., when the number of commands to be processed by the systemcontroller 130 is small, when there are no commands to be processed bythe system controller 130, when the access frequency at which theactuator 16 is driven and the head 15 accesses the disk 10 is small, orwhen the system controller 130 is in an idle state, that is, when thesystem controller 130 is not in a busy state. The “access frequency”means the number of times the head accesses a particular region within aparticular time is large (high access frequency) or the number of timesthe head accesses a particular region within a particular time is small(low access frequency).

When the system controller 130A is not in a busy state, the internal logmanagement unit 620A writes an internal log table corresponding toanother actuator 16 (another disk 10 other than the disk 10A, anotherhead 15 other than the head 15A, or another controller 130 other thanthe system controller 130A) or the like, other than the actuator 16A,controlled by another system controller 130, other than the systemcontroller 130A, which is in a busy state, for example, the internal logtable TBB corresponding to the actuator 16B (the disk 10B, the head 15B,and the system controller 130B) described later, to the non-volatilerecording region, for example, to the system area 10A2 of disk 10A. Whenthe system controller 130A is not in a busy state, the internal logmanagement unit 620A may write the internal log table TBA to thenon-volatile recording region, for example, the system area 10A2 of thedisk 10A.

When the power of the magnetic disk device 1 is turned off, or when thepower of the magnetic disk device 1 is cut off, the internal logmanagement unit 620A clears the ATI count corresponding to each track ofthe disk 10A included in the internal log table TBA, for example, theATI management table TBA, recorded in the volatile recording region, forexample, the volatile memory 70 or the like, for example, makes the ATIcount zero.

When the power of the magnetic disk device 1 is turned on (hereinafter,may be referred to as startup), the internal log management unit 620Adetects the time-stamp added to the internal log table TBA correspondingto the actuator 16A (the disk 10A, the head 15A, and the systemcontroller 130A) recorded in all non-volatile recording regions, forexample, all system areas of the disk 10, and generates (constructs orreconstructs) an internal log table including the newest (for example,largest) time-stamp in a volatile recording region, for example, thevolatile memory 70. The internal log management unit 620A may update theinternal log table TBA recorded in all or part of the non-volatilerecording region, for example, the system area of the disk 10, to theinternal log table TBA generated (constructed or reconstructed) in thevolatile recording region, for example, the volatile memory 70 atstartup.

The refresh processing unit 630A once reads the data written to theparticular recording region, and performs a process of rewriting theread data to the particular recording region (hereinafter, may bereferred to as a refresh process). The refresh processing unit 630Arefers to the internal log table TBA corresponding to the ATI managementtable, and when the ATI count corresponding to a particular track of thedisk 10A exceeds a particular threshold (hereinafter, may be referred toas a refresh threshold), performs a refresh process on this track.

The system controller (controller) 130B includes an R/W channel 40B, ahard disk controller (HDC) 50B, and an MPU 60B. The system controller130B is electrically connected to, for example, the driver IC 20, thehead amplifier IC 30, the system controller 130A, and the like. Thesystem controller 130B is electrically connected to the volatile memory70, the nonvolatile memory 80, the buffer memory 90, the host 100, andthe like via the system controller 130A.

The R/W channel 40B executes a signal process of read data transferredfrom the disk 10B to the host 100 and write data transferred from thehost 100 in response to an instruction from the MPU 60B to be describedlater. The R/W channel 40B has a circuit or a function of measuring asignal quality of read data. The R/W channel 40B is electricallyconnected to the head amplifier IC 30, the HDC 50B, the MPU 60B, and thelike, for example.

The HDC 50B controls data transfer between the host 100 and the R/Wchannel 40B via the HDC 50A in response to an instruction from the MPU60B described later. The HDC 50B is electrically connected to, forexample, the R/W channel 40B, the MPU 60B, and the system controller130A (HDC 50A).

The MPU 60B is a controller that controls respective units of themagnetic disk device 1. The MPU 60B controls the actuator 16B (VCM 14B)via the driver IC 20 and executes servo control that positions the head15B. The MPU 60B controls a write operation of the data to the disk 10Band selects the storage destination of the write data. In addition, theMPU 60B controls a read operation of the data from the disk 10B andcontrols the process of the read data. The MPU 60B is connected torespective units of the magnetic disk device 1. The MPU 60B iselectrically connected to the driver IC 20, the R/W channel 40B, the HDC50B, and the like, for example.

The MPU 60B includes a read/write controller 610B, an internal logmanagement unit 620B, a refresh processing unit 630B, and the like. TheMPU 60B executes the process of each of these units, for example, theread/write controller 610B, the internal log management unit 620B, therefresh processing unit 630B, and the like on the firmware. The MPU 60Bmay include the respective units, for example, the read/write controller610B, the internal log management unit 620B, the refresh processing unit630B, and the like as circuits.

The read/write controller 610B controls the read process and the writeprocess of data according to a command from the host 100. The read/writecontroller 610B controls the VCM 14 via the driver IC 20, positions thehead 15B at a target position on the disk 10B, and reads or writes data.

The internal log management unit 620B manages the internal log. Theinternal log management unit 620B manages the internal log as a table.The internal log management unit 620B develops (disposes or temporarilystores) the internal log table TBB corresponding to the actuator 16B(the disk 10B, the head 15B, and the system controller 130B) in avolatile recording region, for example, volatile memory 70, to perform aprocess such as updating. For example, when the internal log table TBBis the ATI management table, every time data is written to a tracklocated in the radial direction of a particular track, for example, toan adjacent track adjacent to the particular track, a particular numberof times, for example, once, the internal log management unit 620Bincreases the ATI count corresponding to this track of the internal logtable TBB developed to the volatile memory 70 by a particular value, forexample, by one. When the internal log table TBB is the ATI managementtable, and the data is written to the particular track, the internal logmanagement unit 620B clears the ATI count corresponding to thisparticular track of the internal log table TBB developed to the volatilememory 70, for example, makes the ATI count zero.

The internal log management unit 620B periodically records the internallog table TBB developed to the volatile recording region, for example,the volatile memory 70, in the non-volatile recording region, forexample, the system area 10B2 of the disk 10B. When the internal logmanagement unit 620B records the internal log table TBB developed in thevolatile recording region, for example, the volatile memory 70, in thenon-volatile recording region, for example, the system area 10B2 of thedisk 10B, the internal log management unit 620B adds a time-stamp to theinternal log table TBB and record it in the system area 10B2 of the disk10B.

When the system controller 130B is in a busy state, the internal logmanagement unit 620B writes the internal log table TBB to a system areaof another disk 10, other than the disk 10B, for example, the systemarea 10A2 of the disk 10A, corresponding to a system controller 130 thatis not in a busy state.

When the system controller 130B is not in a busy state, the internal logmanagement unit 620B writes an internal log table corresponding toanother actuator 16 (another disk other than the disk 10B, another headother than the head 15B, or another system controller other than thesystem controller 130B) or the like, other than the actuator 16B,controlled by another system controller 130, other than the systemcontroller 130B, which is in a busy state, for example, the internal logtable TBA corresponding to the actuator 16A (the disk 10A, the head 15A,and the system controller 130A), to the non-volatile recording region,for example, to the system area 10B2 of disk 10B. When the systemcontroller 130B is not in a busy state, the internal log management unit620B may write the internal log table TBB to a non-volatile recordingregion, for example, the system area 10B2 of the disk 10B.

When the power of the magnetic disk device 1 is turned off, or when thepower of the magnetic disk device 1 is cut off, the internal logmanagement unit 620B clears the ATI count corresponding to each track ofthe disk 10B included in the internal log table TBB, for example, theATI management table TBB, recorded in the volatile recording region, forexample, the volatile memory 70 or the like, for example, makes the ATIcount zero.

When the power of the magnetic disk device 1 is turned on, the internallog management unit 620B detects the time-stamp added to the internallog table TBB corresponding to the actuator 16B (the disk 10B, the head15B, and the system controller 130B) recorded in all non-volatilerecording regions, for example, all system areas of the disk 10, andgenerates (constructs or reconstructs) an internal log table includingthe newest (for example, largest) time-stamp in a volatile recordingregion, for example, the volatile memory 70. The internal log managementunit 620B may update the internal log table TBB recorded in all or partof the non-volatile recording region, for example, the system area ofthe disk 10, to the internal log table TBB generated (constructed orreconstructed) in the volatile recording region, for example, thevolatile memory 70 at startup.

The refresh processing unit 630B performs the refresh process. Therefresh processing unit 630B refers to the internal log table TBBcorresponding to the ATI management table, and when the ATI countcorresponding to a particular track of the disk 10B exceeds the refreshthreshold, performs a refresh process on this track.

FIG. 3 is a schematic diagram showing an example of the ATI count to beincreased for the surrounding region according to the number of timesdata is written to a particular track 0. The horizontal axis indicatesthe track position relative to the track to which data was written, andthe vertical axis indicates the ATI count to be increased when the datais written once to the track corresponding to 0 on the horizontal axis.FIG. 3 shows a line of a plurality of ATI counts measured with aplurality of heads with different characteristics.

In the example shown in FIG. 3, when data is written to a particulartrack once, one is added to the ATI count of the at least adjacenttrack.

FIG. 4 is a schematic diagram showing an example of the internal logtables TBA and TBB. In FIG. 4, the internal log tables TBA and TBBcorrespond to the ATI management table.

In the example shown in FIG. 4, the internal log table (ATI managementtable) TBA and TBB includes the head (HEAD) numbers, the time-stamp[sec], and the ATI count corresponding to each cylinder (track) of eachdisk 10A and 10B.

FIG. 5 is a schematic diagram showing an example of the managementmethod of the internal log tables TBA and TBB according to the presentembodiment.

In the example shown in FIG. 5, when the system controller 130A is in abusy state at the timing of recording the internal log table TBAdeveloped in the volatile memory 70 in the system area 10A2 of the disk10A, the system controller 130A records the internal log table TBA towhich a time-stamp is added in the system area 10B2 of the disk 10B viathe system controller 130B which is not in a busy state.

In the example shown in FIG. 5, when the system controller 130B is in abusy state at the timing of recording the internal log table TBBdeveloped in the volatile memory 70 in the system area 10B2 of the disk10B, the system controller 130B records the internal log table TBB towhich a time-stamp is added in the system area 10A2 of the disk 10A viathe system controller 130A which is not in a busy state.

FIG. 6 is a schematic diagram showing an example of the managementmethod of the internal log tables TBA and TBB according to the presentembodiment.

In the example shown in FIG. 6, when the system controller 130A is notin a busy state at the timing of recording the internal log table TBAdeveloped in the volatile memory 70 in the system area 10A2 of the disk10A, the system controller 130A records the internal log table TBA towhich a time-stamp is added in the system area 10A2 of the disk 10A.

In the example shown in FIG. 6, when the system controller 130A is in abusy state at the timing of recording the internal log table TBAdeveloped in the volatile memory 70 in the system area 10A2 of the disk10A, the system controller 130A records the internal log table TBA towhich a time-stamp is added in the system area 10B2 of the disk 10B viathe system controller 130B which is not in a busy state.

In the example shown in FIG. 6, when the system controller 130B is notin a busy state at the timing of recording the internal log table TBBdeveloped in the volatile memory 70 in the system area 10B2 of the disk10B, the system controller 130B records the internal log table TBB towhich a time-stamp is added in the system area 10B2 of the disk 10B.

In the example shown in FIG. 6, when the system controller 130B is in abusy state at the timing of recording the internal log table TBBdeveloped in the volatile memory 70 in the system area 10B2 of the disk10B, the system controller 130B records the internal log table TBB towhich a time-stamp is added in the system area 10A2 of the disk 10A viathe system controller 130A which is not in a busy state.

FIG. 7 is a flowchart showing an example of the management method of theinternal log table according to the present embodiment.

The system controller 130 reads the internal log table (hereinafter, maybe referred to as a target internal log table) corresponding to anactuator (hereinafter, may be referred to as a target actuator) 16controlled by a target system controller (hereinafter, may be referredto as a target system controller) 130, a disk 10 corresponding to thetarget system controller 130 (hereinafter, may be referred to as atarget disk 10), and a head 15 corresponding to the target systemcontroller 130 (hereinafter, may be referred to as a target head 15),and the like from a particular non-volatile recording region, forexample, the system area, of all disks 10 (B701). The system controller130 develops (or constructs) the newest target internal log table amongthe plurality of target internal log tables recorded in a particularnon-volatile recording region, for example, the system area, of theplurality of disks 10 in a particular volatile recording region, forexample, the volatile memory 70 (B702). For example, the systemcontroller 130 develops (or constructs) the target internal log tablehaving the largest time-stamp among the plurality of target internal logtables recorded in a particular non-volatile recording region, forexample, the system area, of the plurality of disks 10 in a particularvolatile recording region, for example, the volatile memory 70. Thesystem controller 130 determines whether the target system controller130 is in a busy state or not (B703). When it is determined that thetarget system controller 130 is not in a busy state (No in B703), thesystem controller 130 writes the target internal log table,corresponding to the target system controller 130, recorded in aparticular volatile recording region, for example, the volatile memory70, to a particular non-volatile recording region, for example, thesystem area, of the target disk 10 (B704), and ends the process. When itis determined that the target system controller 130 is in a busy state(Yes in B703), the system controller 130 writes the target internal logtable recorded in a particular volatile recording region, for example,the volatile memory 70 to a particular non-volatile recording region,for example, the system area, of another disk, other than the targetdisk 10, corresponding to another actuator 16, other than the targetactuator 16, controlled by another system controller 130, other than thetarget system controller 130, in which the target system controller 130is not in a busy state (B705), and ends the process.

According to the embodiment when the target system controller 130 is ina busy state, the magnetic disk device 1 records the target internal logtable corresponding to the target disk 10, the target head 15, thetarget actuator 16, the target system controller 130, and the like inthe system area of another disk 10, other than the target disk 10,corresponding to another system controllers 130, other than the targetsystem controller 130, which is not in a busy state. When started afterthe power is turned off, or after the power is cut off, the magneticdisk device 1 can generate (constructs or reconstructs) the targetinternal log table in the volatile memory 70 based on the targetinternal log table corresponding to the target disk 10, the target head15, the target actuator 16, the target system controller 130, and thelike recorded in the system area of the particular disk 10. Therefore,the magnetic disk device 1 can improve the reliability of data whilemaintaining the performance of write/read processing.

Next, a magnetic disk device according to modifications of theembodiment will be described. In the modifications, the same referencenumerals are attached to the same parts as those in the aboveembodiment, and a detailed description thereof will be omitted.

Modification 1

The magnetic disk device 1 according to Modification 1 has a differentnumber of actuators from the magnetic disk device 1 of theabove-described embodiment.

The disk 10 has, for example, disks 10A, 10B, and 10C. The disk 10 mayhave four or more disks. Further, the disk 10C may have two or moredisks. The head 15 has, for example, heads 15A, 15B, and 15C. The head15 may have four or more heads. Further, the head 15C may have two ormore heads.

The actuator 16 has actuators 16A, 16B, and 16C. The actuator 16 mayhave four or more actuators. The actuator 16C is mounted on a commonpivot and can rotate independently around the pivot. The actuator 16Ccontrols the movement of the head 15C mounted on the arm to a particularposition on the disk 10C by driving the VCM. The actuator 16C mayinclude the head 15C, the driver IC 20, and the head amplifier IC 30.

In the disk 10, a user data region that can be used by a user and asystem area to which information necessary for the system management iswritten are allocated in a region to which the data can be written. Forexample, the disk 10A is allocated a user data region 10A1 and a systemarea 10A2. For example, the disk 10B is allocated a user data region10B1 and a system area 10B2. Hereinafter, a direction orthogonal to theradial direction of the disk 10 is referred to as a circumferentialdirection.

The system controller 130 includes, for example, system controllers130A, 130B, and 130C. For example, the system controller 130C iselectrically connected to the driver IC 20, the head amplifier IC 30,and the system controller 130B. The system controller 130 may have fouror more system controllers 130.

FIG. 8 is a schematic diagram showing a configuration example of thesystem controller 130 according to Modification 1.

The system controller (controller) 130C includes a read/write (R/W)channel 40C, an HDC 50C, and an MPU 60C. The system controller 130C iselectrically connected to the driver IC 20, the head amplifier IC 30,the volatile memory 70, the nonvolatile memory 80, the buffer memory 90,the system controller 130B, and the like.

The R/W channel 40C executes a signal process of read data transferredfrom the disk 10C to the host 100 and write data transferred from thehost 100 in response to an instruction from the MPU 60C to be describedlater. The R/W channel 40C has a circuit or a function of measuring asignal quality of read data. The R/W channel 40C is electricallyconnected to the head amplifier IC 30, the HDC 50C, the MPU 60C, and thelike, for example.

The HDC 50C controls data transfer between the host 100 and the R/Wchannel 40C in response to an instruction from the MPU 60C describedlater. The HDC 50C is electrically connected to, for example, the R/Wchannel 40C, the MPU 60C, the system controller 130B, and the like.

The MPU 60C is a main controller that controls respective units of themagnetic disk device 1. The MPU 60C controls the actuator 16C (VCM) viathe driver IC 20 and executes servo control that positions the head 15C.The MPU 60C controls a write operation of the data to the disk 10C andselects the storage destination of the write data. In addition, the MPU60C controls a read operation of the data from the disk 10C and controlsthe process of the read data. The MPU 60C is connected to respectiveunits of the magnetic disk device 1. The MPU 60C is electricallyconnected to the driver IC 20, the R/W channel 40C, the HDC 50C, and thelike, for example.

The MPU 60C includes a read/write controller 610C, an internal logmanagement unit 620C, and a refresh processing unit 630C. The MPU 60Cexecutes process of each of these units, such as the read/writecontroller 610C, the internal log management unit 620C, and the refreshprocessing unit 630C, on the firmware. The MPU 60C may include therespective units, for example, the read/write controller 610C, theinternal log management unit 620C, the refresh processing unit 630C, andthe like as circuits.

The read/write controller 610C controls the read process and the writeprocess of data according to a command from the host 100. The read/writecontroller 610C controls the VCM 14 via the driver IC 20, positions thehead 15C at a target position on the disk 10C, and reads or writes data.

The internal log management unit 620C manages the internal log. Theinternal log management unit 620C manages the internal log as a table.The internal log management unit 620C develops (disposes or temporarilystores) the internal log table TBC corresponding to the actuator 16C(the disk 10C, the head 15C, and the system controller 130C) in avolatile recording region, for example, the volatile memory 70, toperform a process such as updating. For example, when the internal logtable TBC is the ATI management table, every time data is written to atrack located in the radial direction of a particular track, forexample, to an adjacent track adjacent to the particular track, aparticular number of times, for example, once, the internal logmanagement unit 620C increases the ATI count corresponding to this trackof the internal log table TBC developed to the volatile memory 70 by aparticular value, for example, by one.

The internal log management unit 620C periodically records the internallog table TBC developed to the volatile recording region, for example,the volatile memory 70, in the non-volatile recording region, forexample, the system area 10C2 of the disk 10C. When the internal logmanagement unit 620C records the internal log table TBC developed in thevolatile recording region, for example, the volatile memory 70, in thenon-volatile recording region, for example, the system area 10C2 of thedisk 10C, the internal log management unit 620C adds a time-stamp to theinternal log table TBC and record it in the system area 10C2 of the disk10C.

When the system controller 130C is in a busy state, the internal logmanagement unit 620C writes the internal log table TBC to a system areaof another disk 10, other than the disk 10C, corresponding to the systemcontroller 130 that is not in a busy state, for example, the system area10A2 of the disk 10A and/or the system area 10B2 of the disk 10B.

When the system controller 130C is not in a busy state, the internal logmanagement unit 620C writes an internal log table corresponding toanother actuator 16 (another disk 10 other than the disk 10C, anotherhead 15 other than the head 15C, or another controller 130 other thanthe system controller 130C) or the like, other than the actuator 16C,controlled by another system controller 130, other than the systemcontroller 130C, which is in a busy state, for example, the internal logtable TBC corresponding to the actuator 16C (the disk 10C, the head 15C,and the system controller 130C) described later, to the non-volatilerecording region, for example, the system area 10C2 of disk 10C. Whenthe system controller 130C is not in a busy state, the internal logmanagement unit 620C may write the internal log table TBC to anon-volatile recording region, for example, the system area 10C2 of thedisk 10C.

When the power of the magnetic disk device 1 is turned off, or when thepower of the magnetic disk device 1 is cut off, the internal logmanagement unit 620C clears the ATI count corresponding to each track ofthe disk 10C included in the internal log table TBC, for example, theATI management table TBC, recorded in the volatile recording region, forexample, the volatile memory 70 or the like, for example, makes the ATIcount zero.

When the power of the magnetic disk device 1 is turned on, the internallog management unit 620C detects the time-stamp added to the internallog table TBC corresponding to the actuator 16C (the disk 10C, the head15C, and the system controller 130C) recorded in all non-volatilerecording regions, for example, all system areas of the disk 10, andgenerates (constructs or reconstructs) an internal log table includingthe newest (for example, largest) time-stamp in a volatile recordingregion, for example, the volatile memory 70. The internal log managementunit 620C may update the internal log table TBC recorded in all or partof the non-volatile recording region, for example, the system area ofthe disk 10, to the internal log table TBC generated (constructed orreconstructed) in the volatile recording region, for example, thevolatile memory 70 at startup.

The refresh processing unit 630C performs the refresh process. Therefresh processing unit 630C refers to the internal log table TBCcorresponding to the ATI management table, and when the ATI countcorresponding to a particular track of the disk 10C exceeds the refreshthreshold, performs a refresh process on this track.

FIG. 9 is a schematic diagram showing an example of the managementmethod of the internal log tables TBA, TBB, and TBC according toModification 1.

In the example shown in FIG. 9, when the system controller 130A is in abusy state at the timing of recording the internal log table TBAdeveloped in the volatile memory 70 in the system area 10A2 of the disk10A, the system controller 130A records the internal log table TBA towhich a time-stamp is added in the system area 10B2 of the disk 10B viathe system controller 130B which is not in a busy state.

In the example shown in FIG. 9, when the system controller 130B is in abusy state at the timing of recording the internal log table TBBdeveloped in the volatile memory 70 in the system area 10B2 of the disk10B, the system controller 130B records the internal log table TBB towhich a time-stamp is added in the system area 10C2 of the disk 10C viathe system controller 130C which is not in a busy state.

In the example shown in FIG. 9, when the system controller 130C is in abusy state at the timing of recording the internal log table TBCdeveloped in the volatile memory 70 in the system area 10C2 of the disk10C, the system controller 130C records the internal log table TBC towhich a time-stamp is added in the system area 10A2 of the disk 10A viathe system controller 130A which is not in a busy state.

FIG. 10 is a schematic diagram showing an example of the managementmethod of the internal log tables TBA, TBB, and TBC according toModification 1.

In the example shown in FIG. 10, when the system controller 130A is in abusy state at the timing of recording the internal log table TBAdeveloped in the volatile memory 70 in the system area 10A2 of the disk10A, the system controller 130A records the internal log table TBA towhich a time-stamp is added in the system area 10B2 of the disk 10B viathe system controller 130B which is not in a busy state.

In the example shown in FIG. 10, when the system controller 130A is in abusy state at the timing of recording the internal log table TBAdeveloped in the volatile memory 70 in the system area 10A2 of the disk10A, the system controller 130A records the internal log table TBA towhich a time-stamp is added in the system area 10C2 of the disk 10C viathe system controller 130C which is not in a busy state.

In the example shown in FIG. 10, when the system controller 130B is in abusy state at the timing of recording the internal log table TBBdeveloped in the volatile memory 70 in the system area 10B2 of the disk10B, the system controller 130B records the internal log table TBB towhich a time-stamp is added in the system area 10C2 of the disk 10C viathe system controller 130C which is not in a busy state.

In the example shown in FIG. 10, when the system controller 130B is in abusy state at the timing of recording the internal log table TBBdeveloped in the volatile memory 70 in the system area 10B2 of the disk10B, the system controller 130B records the internal log table TBB towhich a time-stamp is added in the system area 10A2 of the disk 10A viathe system controller 130A which is not in a busy state.

In the example shown in FIG. 10, when the system controller 130C is in abusy state at the timing of recording the internal log table TBCdeveloped in the volatile memory 70 in the system area 10C2 of the disk10C, the system controller 130C records the internal log table TBC towhich a time-stamp is added in the system area 10A2 of the disk 10A viathe system controller 130A which is not in a busy state.

In the example shown in FIG. 10, when the system controller 130C is in abusy state at the timing of recording the internal log table TBCdeveloped in the volatile memory 70 in the system area 10C2 of the disk10C, the system controller 130C records the internal log table TBC towhich a time-stamp is added in the system area 10B2 of the disk 10B viathe system controller 130B which is not in a busy state.

FIG. 11 is a schematic diagram showing an example of the managementmethod of the internal log tables TBA, TBB, and TBC according toModification 1.

In the example shown in FIG. 11, when the system controller 130A is notin a busy state at the timing of recording the internal log table TBAdeveloped in the volatile memory 70 in the system area 10A2 of the disk10A, the system controller 130A records the internal log table TBA towhich a time-stamp is added in the system area 10A2 of the disk 10A.

In the example shown in FIG. 11, when the system controller 130A is in abusy state at the timing of recording the internal log table TBAdeveloped in the volatile memory 70 in the system area 10A2 of the disk10A, the system controller 130A records the internal log table TBA towhich a time-stamp is added in the system area 10B2 of the disk 10B viathe system controller 130B which is not in a busy state.

In the example shown in FIG. 11, when the system controller 130A is in abusy state at the timing of recording the internal log table TBAdeveloped in the volatile memory 70 in the system area 10A2 of the disk10A, the system controller 130A records the internal log table TBA towhich a time-stamp is added in the system area 10C2 of the disk 10C viathe system controller 130C which is not in a busy state.

In the example shown in FIG. 11, when the system controller 130B is notin a busy state at the timing of recording the internal log table TBBdeveloped in the volatile memory 70 in the system area 10B2 of the disk10B, the system controller 130B records the internal log table TBB towhich a time-stamp is added in the system area 10B2 of the disk 10B.

In the example shown in FIG. 11, when the system controller 130B is in abusy state at the timing of recording the internal log table TBBdeveloped in the volatile memory 70 in the system area 10B2 of the disk10B, the system controller 130B records the internal log table TBB towhich a time-stamp is added in the system area 10C2 of the disk 10C viathe system controller 130C which is not in a busy state.

In the example shown in FIG. 11, when the system controller 130B is in abusy state at the timing of recording the internal log table TBBdeveloped in the volatile memory 70 in the system area 10B2 of the disk10B, the system controller 130B records the internal log table TBB towhich a time-stamp is added in the system area 10A2 of the disk 10A viathe system controller 130A which is not in a busy state.

In the example shown in FIG. 11, when the system controller 130C is notin a busy state at the timing of recording the internal log table TBCdeveloped in the volatile memory 70 in the system area 10C2 of the disk10C, the system controller 130C records the internal log table TBC towhich a time-stamp is added in the system area 10C2 of the disk 10C.

In the example shown in FIG. 11, when the system controller 130C is in abusy state at the timing of recording the internal log table TBCdeveloped in the volatile memory 70 in the system area 10C2 of the disk10C, the system controller 130C records the internal log table TBC towhich a time-stamp is added in the system area 10A2 of the disk 10A viathe system controller 130A which is not in a busy state.

In the example shown in FIG. 11, when the system controller 130C is in abusy state at the timing of recording the internal log table TBCdeveloped in the volatile memory 70 in the system area 10C2 of the disk10C, the system controller 130C records the internal log table TBC towhich a time-stamp is added in the system area 10B2 of the disk 10B viathe system controller 130B which is not in a busy state.

According to Modification 1, the magnetic disk device 1 can improve thereliability of data while maintaining the performance of write/readprocessing.

An example of the magnetic disk device and the information managementmethod obtained from the configuration disclosed in the presentspecification is added below.

(1) A magnetic disk device includes a first disk having a first userdata region to which user data is written and a first system areadifferent from the first user data region, a second disk having a seconduser data region to which user data is written and a second system areadifferent from the second user data region, a first head that writesdata to the first disk and that reads data from the first disk, a secondhead that writes data to the second disk and that reads data from thesecond disk, a first actuator having the first head, a second actuatorhaving the second head, a first controller that controls the first disk,the first head, and the first actuator, and a second controller thatcontrols the second disk, the second head, and the second actuator,wherein the first controller records first information related to thefirst head and the first disk in the second system area.

(2) The magnetic disk device according to (1), wherein the firstcontroller records the first information in the first system area.

(3) The magnetic disk device according to (2), further including avolatile memory, wherein the first controller records the firstinformation in the volatile memory.

(4) The magnetic disk device according to (3), wherein the firstcontroller periodically records the first information that is updatedwith the volatile memory and to which a time-stamp is added in at leastone of the first system area and the second system area.

(5) The magnetic disk device according to (4), wherein when the numberof commands to be processed by the first controller is large, and whenthe number of commands to be processed by the second controller issmall, the first controller records the first information that isupdated with the volatile memory and to which a time-stamp is added inthe second system area.

(6) The magnetic disk device according to (5), wherein when the numberof commands to be processed by the first controller is small, the firstcontroller records the first information that is updated with thevolatile memory and to which a time-stamp is added in the first systemarea.

(7) The magnetic disk device according to (6), wherein at startup, thefirst controller records the first information having a largertime-stamp among the first information recorded in the first system areaand the first information recorded in the second system area in thevolatile memory.

(8) The magnetic disk device according to any one of (1) to (7), whereinthe first information corresponds to a table showing a degree ofinfluence of a leakage magnetic flux according to the number of timesdata is written to a region adjacent to the first disk in a radialdirection.

(9) The magnetic disk device according to any one of (1) to (8), whereinthe second controller records the second information related to thesecond head and the second disk in the first system area.

(10) The magnetic disk device according to (9), wherein the secondcontroller records the second information in the volatile memory.

(11) The magnetic disk device according to (10), wherein the secondcontroller periodically records the second information that is updatedwith the volatile memory and to which a time-stamp is added in at leastone of the first system area and the second system area.

(12) The magnetic disk device according to (11), wherein when the numberof commands to be processed by the second controller is large, and whenthe number of commands to be processed by the first controller is small,the second controller records the second information that is updatedwith the volatile memory and to which a time-stamp is added in the firstsystem area.

(13) The magnetic disk device according to (12), wherein when the numberof commands to be processed by the second controller is small, thesecond controller records the second information that is updated withthe volatile memory and to which a time-stamp is added in the secondsystem area.

(14) The magnetic disk device according to (13), wherein at startup, thesecond controller records the second information having a largertime-stamp among the second information recorded in the first systemarea and the second information recorded in the second system area inthe volatile memory.

(15) The magnetic disk device according to any one of (9) to (14),wherein the second information corresponds to a table showing a degreeof influence of a leakage magnetic flux according to the number of timesdata is written to a region adjacent to the disk in a radial direction.

(16) A magnetic disk device includes a plurality of disks each having auser data region to which user data is written and a system areadifferent from the user data region, a plurality of heads that writesdata to the plurality of respective disks and that reads data from theplurality of respective disks, a plurality of actuators having theplurality of respective heads, and a plurality of controllers thatcontrols the plurality of disks, the plurality of heads, and theplurality of actuators, wherein a first controller among the pluralityof controllers records first information related to a first head, amongthe plurality of heads, controlled by the first controller and a firstdisk, among the plurality of disks, which the first head faces in asystem area of another disk, other than the first disk, among theplurality of disks.

(17) In an information management method applied to a magnetic diskdevice including a plurality of disks each having a user data region towhich user data is written and a system area different from the userdata region, a plurality of heads that writes data to the plurality ofrespective disks and that reads data from the plurality of respectivedisks, a plurality of actuators having the plurality of respectiveheads, and a plurality of controllers that controls the plurality ofdisks, the plurality of heads, and the plurality of actuators, themethod includes recording first information related to a first headamong the plurality of heads and a first disk, among the plurality ofdisks, which the first head faces in a system area of another disk,other than the first disk, among the plurality of disks.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A magnetic disk device comprising: a first diskhaving a first user data region to which user data is written and afirst system area different from the first user data region; a seconddisk having a second user data region to which user data is written anda second system area different from the second user data region; a firsthead that writes data to the first disk and that reads data from thefirst disk; a second head that writes data to the second disk and thatreads data from the second disk; a first actuator having the first head;a second actuator having the second head; a first controller thatcontrols the first disk, the first head, and the first actuator; and asecond controller that controls the second disk, the second head, andthe second actuator, wherein the first controller records firstinformation related to the first head and the first disk in the secondsystem area.
 2. The magnetic disk device according to claim 1, whereinthe first controller records the first information in the first systemarea.
 3. The magnetic disk device according to claim 2, furthercomprising: a volatile memory, wherein the first controller records thefirst information in the volatile memory.
 4. The magnetic disk deviceaccording to claim 3, wherein the first controller periodically recordsthe first information, which is updated with the volatile memory and towhich a time-stamp is added, in at least one of the first system areaand the second system area.
 5. The magnetic disk device according toclaim 4, wherein when a number of commands to be processed by the firstcontroller is large, and when a number of commands to be processed bythe second controller is small, the first controller records the firstinformation, which is updated with the volatile memory and to which atime-stamp is added, in the second system area.
 6. The magnetic diskdevice according to claim 5, wherein when the number of commands to beprocessed by the first controller is small, the first controller recordsthe first information, which is updated with the volatile memory and towhich a time-stamp is added, in the first system area.
 7. The magneticdisk device according to claim 6, wherein at startup, the firstcontroller records the first information having a larger time-stampamong the first information recorded in the first system area and thefirst information recorded in the second system area in the volatilememory.
 8. The magnetic disk device according to claim 1, wherein thefirst information corresponds to a table showing a degree of influenceof a leakage magnetic flux according to a number of times data iswritten to a region adjacent to the first disk in a radial direction. 9.The magnetic disk device according to claim 1, wherein the secondcontroller records second information related to the second head and thesecond disk in the first system area.
 10. The magnetic disk deviceaccording to claim 9, wherein the second controller records the secondinformation in the volatile memory.
 11. The magnetic disk deviceaccording to claim 10, wherein the second controller periodicallyrecords the second information, which is updated with the volatilememory and to which a time-stamp is added, in at least one of the firstsystem area and the second system area.
 12. The magnetic disk deviceaccording to claim 11, wherein when a number of commands to be processedby the second controller is large, and when a number of commands to beprocessed by the first controller is small, the second controllerrecords the second information, which is updated with the volatilememory and to which a time-stamp is added, in the first system area. 13.The magnetic disk device according to claim 12, wherein when the numberof commands to be processed by the second controller is small, thesecond controller records the second information, which is updated withthe volatile memory and to which a time-stamp is added, in the secondsystem area.
 14. The magnetic disk device according to claim 13, whereinat startup, the second controller records the second information havinga larger time-stamp among the second information recorded in the firstsystem area and the second information recorded in the second systemarea in the volatile memory.
 15. The magnetic disk device according toclaim 9, wherein the second information corresponds to a table showing adegree of influence of a leakage magnetic flux according to a number oftimes data is written to a region adjacent to the second disk in aradial direction.
 16. A magnetic disk device comprising: a volatilememory; a plurality of disks each having a user data region to whichuser data is written and a system area different from the user dataregion; a plurality of heads that writes data to the respective disksand that reads data from the respective disks; a plurality of actuatorshaving the respective heads; and a plurality of controllers thatcontrols the disks, the heads, and the actuators, wherein a firstcontroller among the controllers records first information related to afirst head, among the heads, controlled by the first controller and afirst disk, among the disks, which the first head faces in a system areaof another disk, other than the first disk, among the disks.
 17. Themagnetic disk device according to claim 16, wherein the first controllerrecords the first information in the system area of the first disk andthe volatile memory.
 18. The magnetic disk device according to claim 17,wherein the first controller periodically records the first information,which is updated with the volatile memory and to which a time-stamp isadded, in at least one of the system areas of the disks.
 19. Aninformation management method applied to a magnetic disk deviceincluding a volatile memory, a plurality of disks each having a userdata region to which user data is written and a system area differentfrom the user data region, a plurality of heads that writes data to therespective disks and that reads data from the respective disks, aplurality of actuators having the respective heads, and a plurality ofcontrollers that controls the disks, the heads, and the actuators, themethod comprising: by a first controller among the controllers,recording first information related to a first head among the heads anda first disk, among the disks, which the first head faces in a systemarea of another disk, other than the first disk, among the disks. 20.The information management method according to claim 19, furthercomprising: by the first controller, recording the first information inthe system area of the first disk and the volatile memory; and by thefirst controller, periodically recording the first information, which isupdated with the volatile memory and to which a time-stamp is added, inat least one of the system areas of the disks.